Compounds having a C—C triple bond

ABSTRACT

Compounds containing at least one C—C triple bond within a chain of at least 3 ring systems which have positive dielectric anisotropy, the use thereof for high-frequency components, liquid-crystalline media containing these compounds, and high-frequency components, in particular antennae, especially for the gigahertz region, containing these media. The liquid-crystalline media serve, for example, for the phase shifting of microwaves for tuneable phased-array antennae.

The present invention relates to compounds containing at least one C—Ctriple bond within a chain of at least 3 ring systems which havepositive dielectric anisotropy, to the use thereof for high-frequencycomponents, to liquid-crystalline media comprising the compounds, and tohigh-frequency components, in particular antennae, especially for thegigahertz region, comprising these media. The liquid-crystalline mediaserve, for example, for the phase shifting of microwaves for tuneable‘phased-array’ antennae.

Liquid-crystalline media have been used for some time in electro-opticaldisplays (liquid crystal displays—LCDs) in order to display information.

However, liquid-crystalline media have recently also been proposed foruse in components for microwave technology, such as, for example, in DE10 2004 029 429 A and in JP 2005-120208 (A).

An industrially valuable application of liquid-crystalline media inhigh-frequency technology is based on their property that theirdielectric properties can be controlled by a variable voltage,particularly for the gigahertz region. Thus, tuneable antennae can bedesigned which contain no moving parts (A. Gaebler, A. Moessinger, F.Goelden, et al., “Liquid Crystal-Reconfigurable Antenna Concepts forSpace Applications at Microwave and Millimeter Waves”, InternationalJournal of Antennas and Propagation, Vol. 2009, Article ID 876989, 7pages, 2009. doi:10.1155/2009/876989).

The publication A. Penirschke, S. Müller, P. Scheele, C. Weil, M.Wittek, C. Hock and R. Jakoby: “Cavity Perturbation Method forCharacterization of Liquid Crystals up to 35 GHz”, 34^(th) EuropeanMicrowave Conference—Amsterdam, 545-548, describes, inter alia, theproperties of the known, liquid-crystalline single substance K15 (MerckKGaA, Germany) at a frequency of 9 GHz.

DE 10 2004 029 429 A (cf. above) describes the use of conventionalliquid-crystal media in microwave technology, inter alia in phaseshifters. Liquid-crystalline media have already been investigatedtherein with respect to their properties in the corresponding frequencyrange.

Compounds containing a C—C triple bond within a chain of 4 benzene ringsarranged in a linear manner are disclosed in the specifications JP05-255151 A and WO 2009/125721 A1. Some of the compounds from JP05-255151 A are provided with fluorine substituents and are used as acomponent of liquid-crystalline media. The compounds disclosed in thesecond specification are only substituted at the ends of the moleculeand serve as a constituent of thin-film transistors.

Liquid-crystalline compounds having very high optical anisotropy andclearly positive values of the dielectric anisotropy are rare to date.Compounds of this type are certain bistolans containing a polar endgroup, as disclosed, for example, in the publications Shin-Tson Wu etal. Jpn. J. Appl. Phys. 1999, 38, 286-288, Shin-Tson Wu et al. Jpn. J.Appl. Phys. 2000, 39, 38-41, JP 10-45642 A and DE 10120024.

However, the compositions or individual compounds known to date aregenerally afflicted with disadvantages. Most of them result, besidesother deficiencies, in disadvantageously high losses and/or inadequatephase shifts or inadequate material quality. Whereas, for example, someindividual compounds do not have favourable liquid-crystalline phasesand have very high melting points, other substances in turn lacksufficiently high values of Δn and.

For use in high-frequency technology, liquid-crystalline media havingparticular, to date rather unusual, non-standard properties, orcombinations of properties, are required.

Thus, novel components for liquid-crystalline media having improvedproperties are necessary. In particular, the loss in the microwave rangemust be reduced and the material quality (η) must be improved.Furthermore, applications in antenna technology take place under in somecases strongly varying outside boundary conditions, such as, forexample, large temperature variations. In particular, there is a need toimprove the low-temperature behaviour of the components.

There is therefore a considerable demand for liquid-crystalline mediahaving suitable properties for corresponding practical applications.

Surprisingly, it has been found that the compounds according to theinvention have low melting points and high clearing points (transitionfrom the nematic phase into the isotropic phase). In theliquid-crystalline range, the compounds are predominantly nematic orsupport the nematic phase. At the same time, the optical anisotropy (Δn)and the dielectric anisotropy ( ) are equally at high positive values,making them highly suitable, for example, for use as high-frequencymedium. It has been found that, with the compounds according to theinvention, it is possible to achieve liquid-crystalline media having abroad nematic phase range, at the same time high values of Δn and, andadvantageous high-frequency properties.

The invention relates to compounds of the formula I,

in which

-   A¹⁻⁵, independently of one another, optionally oriented to both    sides, denote    -   a) 1,4-phenylene, in which one or more, preferably one to two,        CH groups may be replaced by N,    -   b) a radical of the formula

-   -   in which Y denotes S or O,    -   c) trans-1,4-cyclohexylene or cyclohexenylene, in which, in        addition, one or two non-adjacent CH₂ groups may be replaced by        —O— and/or —S—, and in which H may be replaced by F, or    -   d) a radical from the group 1,4-bicyclo[2.2.2]octylene,        cyclobutane-1,3-diyl, spiro[3.3]heptane-2,6-diyl,        thiophene-2,4-diyl or furan-2,4-diyl,    -   and in which, in groups a), b), c) and d),    -   optionally one or more H atoms independently have been replaced        by a group L,        where at least the ring A³ and/or the ring A⁴ where p=1        denote(s) a radical selected from the radicals

-   L denotes Br, Cl, F, CN, —NCS, —SCN, SF₅, C₁-C₁₀ alkyl, C₁-C₁₀    alkoxy, C₃-C₆ cycloalkyl or a mono- or polyfluorinated C₁-C₁₀ alkyl    or alkoxy group,-   R¹ in each case, independently of one another, denotes a halogenated    or unsubstituted alkyl radical having 1 to 15 C atoms, where, in    addition, one or more CH₂ groups in these radicals may each be    replaced, independently of one another, by —C≡C—, —CH═CH—, —CF═CF—,    —CF═CH—, —CH═CF—, —(CO)O—, —O(CO)—, —(CO)—, —O— or —S— in such a way    that O or S atoms are not linked directly to one another,-   or F, Cl, Br, CN, CF₃, OCF₃, SCN, NCS or SF₅,-   X denotes F, Cl, Br, CN, SCN, NCS, SF₅ or a halogenated alkyl    radical having 1 to 15 C atoms, where, in addition, one or more CH₂    groups in this radical may each be replaced, independently of one    another, by —C≡C—, —CH═CH—, —CF═CF—, —CF═CH—, —CH═CF—, —(CO)O—,    —O(CO)—, —(CO)—, —O— or —S— in such a way that O or S atoms are not    linked directly to one another,-   Z¹, Z², Z⁴, Z⁵, independently of one another, denote a single bond,    —C≡C—, —CH═CH—, —CH₂O—, —(CO)O—, —CF₂O—, —CF₂CF₂—, —CH₂CF₂—,    —CH₂CH₂—, —(CH₂)₄—, —CH═CF— or —CF═CF—, where asymmetrical bridges    may be oriented to both sides, and-   m, n, p, q independently denote 0 or 1, where m+n+p+q is 1, 2, 3 or    4, preferably 1, 2 or 3, particularly preferably 1 or 2.

The optional double bonds of the formula —C(H/F)═CF— in the groupsZ^(1/2/4/5) between the rings A¹ to A⁵ preferably have the transconfiguration (E configuration).

The compounds according to the invention have a comparatively very lowmelting point, a high clearing point, high optical anisotropy (Δn) andclearly positive dielectric anisotropy. The undesired rotation of thecompounds is restricted, making them particularly suitable for use inthe gigahertz region. The relatively low loss factor in the microwavespectrum is advantageous. The compounds have, alone or in a mixture withfurther mesogenic components, a nematic phase over a broad temperaturerange. The totality of these properties make them particularly suitablefor use in components for high-frequency technology, in particular inliquid-crystalline phase shifters. Liquid-crystalline media according tothe invention have the corresponding properties.

Preferred compounds of the formula I are characterised by the choice ofone or more of the following parameters:

The index p is particularly preferably 1. The sum of the indices m+n ispreferably 0 or 1, particularly preferably 0. The sum of the indices p+qis preferably 0, 1 or 2, particularly preferably 2. The total number ofring systems in formula I is therefore 2+m+n+p+q, preferably 3, 4, 5 or6, particularly preferably 3, 4 or 5, and in particular 4.

The groups A¹, A², A³, A⁴ and A⁵ preferably include ring groups inaccordance with definition a), b) or c), particularly preferably ringgroups in accordance with definition a) or b), and very particularlypreferably in accordance with definition a).

The ring groups in accordance with definition a) preferably have thepart-structure

in which L independently denotes Br, Cl, F, CN, —NCS, —SCN, SF₅, C₁-C₁₀alkyl, C₁-C₁₀ alkoxy, C₃-C₆ cycloalkyl or a mono- or polyfluorinatedC₁-C₁₀ alkyl or alkoxy group.

The group A³ preferably has a part-structure selected from the followingformulae:

and/orthe group A⁴, if present (p=1), preferably has a part-structure selectedfrom the following formulae:

Particularly preferred part-structures “-A³-≡-A⁴-” here are selectedfrom the following part-structures:

Preferred compounds of the formula I are those in which the head groupis a group selected from the following formulae:

The bridging groups Z^(1/2/4/5) are preferably, independently of oneanother, a single bond, —C≡C—, —CF═CF— or —CH═CH—, particularlypreferably a single bond.

R¹ preferably denotes a straight-chain alkyl radical having 1 to 15 Catoms, where, in addition, one or more CH₂ groups in these radicals mayeach be replaced, independently of one another, by —C≡C—, —CH═CH—,—(CO)O—, —O(CO)—, —(CO)—, —O— in such a way that O atoms are not linkeddirectly to one another. The group R¹ is preferably an alkyl radicalhaving 2 to 7 C atoms.

The group X preferably denotes F, Cl, Br, CN, CF₃, OCF₃, SCN, NCS, SF₅or a (different) halogenated alkyl radical having 1 to 7 C atoms, where,in addition, one or more CH₂ groups in this radical may each bereplaced, independently of one another, by —C≡C—, —CH═CH—, —CF═CF—,—CF═CH—, —CH═CF—, —(CO)O—, —O(CO)—, —(CO)—, —O— or —S—. The group Xparticularly preferably denotes F, Cl, Br, CN, NCS, SCN, SF₅,fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms (forexample CF₃ or OCF₃) or fluorinated alkenyl, fluorinated alkenyloxy (forexample —OCF═CF₂) or fluorinated alkoxyalkyl having 2 to 7 C atoms, veryparticularly preferably fluorinated alkoxy, fluorinated alkenyloxy, F orCl.

The group L preferably denotes methyl, ethyl, propyl, cyclopropyl or Cl.

Preferred embodiments of the invention are therefore represented by thefollowing illustrative structures:

in which R¹ is as defined in formula I, and in particular R¹ denotes analkyl radical having 2 to 7 C atoms, for example a propyl radical or abutyl, pentyl or hexyl radical.

The compounds of the formula I are prepared by methods known per se, asdescribed in the literature (for example in the standard works, such asHouben-Weyl, Methoden der organischen Chemie [Methods of OrganicChemistry], Georg-Thieme-Verlag, Stuttgart), to be precise underreaction conditions which are known and suitable for the said reactions.Use can also be made here of variants known per se, which are notmentioned here in greater detail.

Typical compounds of the formula I can advantageously be prepared asevident from the following illustrative synthesis schemes (Scheme 1):

R¹ in Scheme 1 has the meaning of R¹ as defined for formula I. ReactionScheme 1 shows the synthesis of certain compounds. The phenyl radicals“R¹-phenyl” can be generalised here to any desired radicals“R¹-(A¹-Z¹)_(m)-(A²-Z²)_(n)-A³-” in accordance with formula I. The otherrings can likewise be varied in type and substitution in accordance withformula I. The parameters L and X are as defined above and below.

The liquid-crystalline media in accordance with the present inventioncomprise one or more compounds of the formula I and optionally at leastone further, preferably mesogenic compound. The liquid-crystal mediumtherefore preferably comprises two or more compounds which arepreferably liquid-crystalline. Preferred media comprise the preferredcompounds of the formula I.

Further components of the liquid-crystalline media are preferablyselected from the compounds of the formula II:

in which

-   L¹¹ denotes R¹¹ or X¹¹,-   L¹² denotes R¹² or X¹²,-   R¹¹ and R¹², independently of one another, denote unfluorinated    alkyl or unfluorinated alkoxy having 1 to 17, preferably having 3 to    10, C atoms or unfluorinated alkenyl, unfluorinated alkynyl,    unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to    15, preferably 3 to 10, C atoms, preferably alkyl or unfluorinated    alkenyl,-   X¹¹ and X¹², independently of one another, denote F, Cl, Br, CN,    NCS, SCN, SF₅, fluorinated alkyl or fluorinated alkoxy having 1 to 7    C atoms or fluorinated alkenyl, fluorinated alkenyloxy or    fluorinated alkoxyalkyl having 2 to 7 C atoms, preferably    fluorinated alkoxy, fluorinated alkenyloxy, F or Cl,-   p, q independently denote 0 or 1,-   Z¹¹ to Z¹³, independently of one another, denote trans-CH═CH—,    trans-CF═CF—, —C≡C— or a single bond, and

-   -   to

-   -   independently of one another, denote

-   -   in which L independently denotes branched or unbranched alkyl,        alkenyl or alkynyl having 1 to 12 C atoms, in which,        independently of one another, one or more “—CH₂—” groups may        also be replaced by 0, or denotes C₃-C₆ cycloalkyl, C₃-C₆        cycloalkenyl, fluorinated alkyl or alkenyl, fluorinated alkoxy        or alkenyloxy,    -   F, Cl, Br, CN, NCS, SCN or SF₅.

In a preferred embodiment of the present invention, theliquid-crystalline media comprise one or more compounds of the formula Iand one or more compounds of the formula II.

The liquid-crystalline media in accordance with the present applicationpreferably comprise in total 5 to 95%, preferably 10 to 90% andparticularly preferably 15 to 80%, of compounds of the formula I.

The liquid-crystalline media in accordance with the present inventionpreferably comprise, more preferably predominantly consist of, even morepreferably essentially consist of and very preferably completely consistof compounds selected from the group of the compounds of the formulae Iand II.

In this application, “comprise” in connection with compositions meansthat the entity in question, i.e. the medium or the component, comprisesthe component or components or compound or compounds indicated,preferably in a total concentration of 10% or more and very preferably20% or more.

In this connection, “predominantly consist of” means that the entity inquestion comprises 55% or more, preferably 60% or more and verypreferably 70% or more, of the component or components or compound orcompounds indicated.

In this connection, “essentially consist of” means that the entity inquestion comprises 80% or more, preferably 90% or more and verypreferably 95% or more, of the component or components or compound orcompounds indicated.

In this connection, “completely consist of” means that the entity inquestion comprises 98% or more, preferably 99% or more and verypreferably 100.0%, of the component or components or compound orcompounds indicated.

The liquid-crystalline media in accordance with the present applicationpreferably comprise in total 10 to 100%, preferably 20 to 95% andparticularly preferably 25 to 90%, of compounds of the formulae I andII.

In accordance with the present invention, the compounds of the formulaII are preferably used in a total concentration of 10% to 90%, morepreferably 15% to 85%, even more preferably 25% to 80% and verypreferably 30% to 75%, of the mixture as a whole.

In addition, the liquid-crystalline media may comprise furtheradditives, such as stabilisers, chiral dopants and nanoparticles. Theindividual, added compounds are employed in concentrations of 0.005 to6%, preferably 0.1 to 3%. The total concentration of these furtherconstituents is in the range from 0% to 10%, preferably 0.1% to 6%,based on the mixture as a whole. However, the concentration data for theremaining constituents of the liquid-crystal mixtures, i.e. theliquid-crystalline or mesogenic compounds, are indicated without takinginto account the concentration of these additives.

The liquid-crystalline media preferably comprise 0 to 10% by weight, inparticular 0.01 to 5% by weight and particularly preferably 0.1 to 3% byweight, of stabilisers. The media preferably comprise one or morestabilisers selected from 2,6-di-tert-butylphenols,2,2,6,6-tetramethylpiperidines or 2-benzotriazol-2-ylphenols. Theseassistants are known to the person skilled in the art and arecommercially available, for example as light stabilisers.

An embodiment of the invention is therefore also a process for thepreparation of a liquid-crystal medium which is characterised in thatone or more compounds of the formula I are mixed with one or morefurther compounds and optionally with one or more additives. The furthercompounds are preferably selected from the compounds of the formula II,as indicated above, and optionally one or more further compounds.

In the present application, the expression dielectrically positivedescribes compounds or components where Δ∈>3.0, dielectrically neutraldescribes those where −1.5≦Δ∈≦3.0 and dielectrically negative describesthose where Δ∈<−1.5. The dielectric anisotropy of the respectivecompound is determined from the results of a solution of 10% of therespective individual compound in a nematic host mixture. If thesolubility of the respective compound in the host mixture is less than10%, the concentration is reduced to 5%. The capacitances of the testmixtures are determined both in a cell having homeotropic alignment andin a cell having homogeneous alignment. The cell thickness of both typesof cells is approximately 20 μm. The voltage applied is a rectangularwave having a frequency of 1 kHz and an effective value of typically 0.5V to 1.0 V, but it is always selected to be below the capacitivethreshold of the respective test mixture.

Δ∈ is defined as (∈_(∥)−∈_(⊥), while ∈_(average) is (∈_(∥)+2∈_(⊥))/3.

The host mixture used for dielectrically positive compounds is mixtureZLI-4792 and that used for dielectrically neutral and dielectricallynegative compounds is mixture ZLI-3086, both from Merck KGaA, Germany.The absolute values of the dielectric constants of the compounds aredetermined from the change in the respective values of the host mixtureon addition of the compounds of interest.

The values are extrapolated to a concentration of the compounds ofinterest of 100%.

Components having a nematic phase at the measurement temperature of 20°C. are measured as such, all others are treated like compounds.

The term threshold voltage in the present application refers to theoptical threshold and is quoted for 10% relative contrast (V₁₀), and theterm saturation voltage refers to the optical saturation and is quotedfor 90% relative contrast (V₉₀), in both cases unless expressly statedotherwise. The capacitive threshold voltage (V₀), also called theFreedericks threshold (V_(Fr)), is only used if expressly mentioned.

The parameter ranges indicated in this application all include the limitvalues, unless expressly stated otherwise.

The different upper and lower limit values indicated for various rangesof properties in combination with one another give rise to additionalpreferred ranges.

Throughout this application, the following conditions and definitionsapply, unless expressly stated otherwise. All concentrations are quotedin percent by weight and relate to the respective mixture as a whole,all temperatures are quoted in degrees Celsius and all temperaturedifferences are quoted in differential degrees. All physical propertiesthat are typical for liquid crystals are determined in accordance with“Merck Liquid Crystals, Physical Properties of Liquid Crystals”, statusNovember 1997, Merck KGaA, Germany, and are quoted for a temperature of20° C., unless expressly stated otherwise. The optical anisotropy (Δn)is determined at a wavelength of 589.3 nm. The dielectric anisotropy(Δ∈) is determined at a frequency of 1 kHz. The threshold voltages, aswell as all other electro-optical properties, are determined using testcells produced at Merck KGaA, Germany. The test cells for thedetermination of Δ∈ have a cell thickness of approximately 20 μm. Theelectrode is a circular ITO electrode having an area of 1.13 cm² and aguard ring. The orientation layers are SE-1211 from Nissan Chemicals,Japan, for homeotropic orientation (∈_(∥)) and polyimide AL-1054 fromJapan Synthetic Rubber, Japan, for homogeneous orientation (∈_(⊥)). Thecapacitances are determined using a Solatron 1260 frequency responseanalyser using a sine wave with a voltage of 0.3 V_(rms). The light usedin the electro-optical measurements is white light. A set-up using acommercially available DMS instrument from Autronic-Melchers, Germany,is used here. The characteristic voltages are determined underperpendicular observation. The threshold (V₁₀), mid-grey (V₅₀) andsaturation (V₉₀) voltages are determined for 10%, 50% and 90% relativecontrast respectively.

The liquid-crystalline media are investigated with respect to theirproperties in the microwave frequency range as described in A.Penirschke et al. “Cavity Perturbation Method for Characterization ofLiquid Crystals up to 35 GHz”, 34^(th) European MicrowaveConference—Amsterdam, pp. 545-548. Compare in this respect also A.Gaebler et al. “Direct Simulation of Material Permittivities . . . ”,12MTC 2009—International Instrumentation and Measurement TechnologyConference, Singapore, 2009 (IEEE), pp. 463-467, and DE 10 2004 029 429A, in which a measurement method is likewise described in detail.

The liquid crystal is introduced into a polytetrafluoroethylene (PTFE)or quartz capillary. The capillary has an internal radius of 180 μm andan external radius of 350 μm. The effective length is 2.0 cm. The filledcapillary is introduced into the centre of the cylindrical cavity with aresonance frequency of 19 GHz. This cavity has a length of 11.5 mm and aradius of 6 mm. The input signal (source) is then applied, and theresult of the output signal is recorded using a commercial vectornetwork analyser. For other frequencies, the dimensions of the cavityare adapted correspondingly.

The change in the resonance frequency and the Q factor between themeasurement with the capillary filled with the liquid crystal and themeasurement without the capillary filled with the liquid crystal is usedto determine the dielectric constant and the loss angle at thecorresponding target frequency by means of equations 10 and 11 in theabove-mentioned publication A. Penirschke et al., 34^(th) EuropeanMicrowave Conference—Amsterdam, pp. 545-548, as described therein.

The values for the components of the properties perpendicular andparallel to the director of the liquid crystal are obtained by alignmentof the liquid crystal in a magnetic field. To this end, the magneticfield of a permanent magnet is used. The strength of the magnetic fieldis 0.35 tesla. The alignment of the magnet is set correspondingly andthen rotated correspondingly through 90°.

The dielectric anisotropy in the microwave region is defined asΔ∈_(r)≡(∈_(r,∥)−∈_(r,⊥)).

The modulatability or tuneability (τ) is defined asτ≡(Δ∈_(r)/∈_(r,∥)).

The material quality (η) is defined asη≡(τ/tan δ_(∈,r,max.)),with the maximum dielectric loss factor tan δ_(∈,r,max.):tan δ_(∈r,max.)≡max. {tan δ_(∈r, ⊥); tan δ_(∈r,∥)}which arises from the maximum value of the measured values for tanδ_(∈r).

The material quality (η) of the preferred liquid-crystal materials is 6or more, preferably 7 or more, preferably 10 or more, preferably 15 ormore, particularly preferably 25 or more and very particularlypreferably 30 or more.

In the corresponding components, the preferred liquid-crystal materialshave phase shifter qualities of 15°/dB or more, preferably 20°/dB ormore, preferably 30°/dB or more, preferably 40°/dB or more, preferably50°/dB or more, particularly preferably 80°/dB or more and veryparticularly preferably 100°/dB or more.

The liquid-crystal media according to the invention preferably havenematic phases of in each case at least from −20° C. to 80° C.,preferably from −30° C. to 85° C. and very particularly preferably from−40° C. to 100° C. The phase particularly preferably extends to 120° C.or more, preferably to 140° C. or more and very particularly preferablyto 180° C. or more. The expression have a nematic phase here means onthe one hand that no smectic phase and no crystallisation are observedat low temperatures at the corresponding temperature and on the otherhand that no clearing occurs on heating from the nematic phase. Theinvestigation at low temperatures is carried out in a flow viscometer atthe corresponding temperature and checked by storage in test cellshaving a cell thickness of 5 μm for at least 100 hours. At hightemperatures, the clearing point is measured in capillaries byconventional methods.

The liquid-crystal media in accordance with the present inventionpreferably have a clearing point of 90° C. or more, more preferably 100°C. or more, even more preferably 120° C. or more, particularlypreferably 150° C. or more and very particularly preferably 170° C. ormore.

The Δ∈ of the liquid-crystal medium in accordance with the invention, at1 kHz and 20° C., is preferably 1 or more, more preferably 2 or more andvery preferably 3 or more.

The Δn of the liquid-crystal media in accordance with the presentinvention, at 589 nm (Na^(D)) and 20° C., is preferably in the rangefrom 0.20 or more to 0.90 or less, more preferably in the range from0.25 or more to 0.90 or less, even more preferably in the range from0.30 or more to 0.85 or less and very particularly preferably in therange from 0.35 or more to 0.80 or less.

In a preferred embodiment of the present application, the Δn of theliquid-crystal media in accordance with the present invention ispreferably 0.50 or more, more preferably 0.55 or more.

Furthermore, the liquid-crystal media according to the invention arecharacterised by high anisotropies in the microwave region. Thebirefringence is, for example, preferably 0.14 or more, particularlypreferably 0.15 or more, particularly preferably 0.20 or more,particularly preferably 0.25 or more and very particularly preferably0.30 or more, at about 8.3 GHz. In addition, the birefringence ispreferably 0.80 or less.

The liquid crystals employed are either single substances or mixtures.They preferably have a nematic phase.

In the present application, the term compounds means both one compoundand a plurality of compounds, unless expressly stated otherwise.

Preferred components which comprise a liquid-crystal medium or at leastone compound in accordance with the invention are phase shifters,varactors, antenna arrays (for example for radio, mobile communications,microwave/radar and other data transmission), ‘matching circuit adaptivefilters’ and others. Preference is given to components forhigh-frequency technology, as defined above. Preference is also given tocomponents which can be modulated by different applied electricalvoltages. Very particularly preferred components are tuneable phaseshifters. In preferred embodiments, a plurality of phase shifters arefunctionally connected, giving, for example, a phase-controlled groupantenna, generally referred to as ‘phased array’ antenna. A groupantenna uses the phase shift of the transmitting or receiving elementsarranged in a matrix in order to achieve bundling through interference.A parallel arrangement of phase shifters in row or grid form enables theconstruction of a so-called ‘phased array’, which can serve as tuneableor passive transmitting or receiving antenna for high frequencies (forexample gigahertz region). Phased-array antennae according to theinvention have a very broad usable reception cone.

Preferred applications are radar installations and data transmissionequipment on manned or unmanned vehicles from the automobile, shipping,aircraft, space travel and satellite technology areas.

For the production of suitable components for high-frequency technology,in particular suitable phase shifters, a liquid-crystalline mediumaccording to the invention is typically introduced into rectangularcavities having a thickness of less than 1 mm, a width of severalmillimeters and a length of several centimeters. The cavities haveopposing electrodes mounted along two long sides. Such arrangements arefamiliar to the person skilled in the art. Through application of avariable voltage, the dielectric properties of the liquid-crystallinemedium can be tuned during operation of the antenna in order to setdifferent frequencies or directions of an antenna.

The expression “halogen” or “halogenated” stands for F, Cl, Br and I,particularly for F and Cl and in particular for F. A halogenated alkylradical therefore preferably means a chlorinated or fluorinated alkylradical.

The expression “alkyl” preferably encompasses straight-chain andbranched alkyl groups having 1 to 15 carbon atoms, in particular thestraight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl andheptyl. Groups having 2 to 10 carbon atoms are generally preferred.

The expression “alkenyl” preferably encompasses straight-chain andbranched alkenyl groups having 2 to 15 carbon atoms, in particular thestraight-chain groups. Particularly preferred alkenyl groups are C₂- toC₇-1E-alkenyl, C₄- to C₇-3E-alkenyl, C₅- to C₇-4-alkenyl, C₆- toC₇-5-alkenyl and C₇-6-alkenyl, in particular C₂- to C₇-1E-alkenyl, C₄-to C₇-3E-alkenyl and C₅- to C₇-4-alkenyl. Examples of further preferredalkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl,1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl,3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl,6-heptenyl and the like. Groups having up to 5 carbon atoms aregenerally preferred.

The expression “alkoxy” preferably encompasses straight-chain radicalsof the formula C_(n)H_(2n+1)—O—, in which n denotes 1 to 10. n ispreferably 1 to 6. Preferred alkoxy groups are, for example, methoxy,ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy,n-nonoxy, n-decoxy.

The expression “oxaalkyl” or “alkoxyalkyl” preferably encompassesstraight-chain radicals of the formula C_(n)H_(2n+1)—O—(CH₂)_(m), inwhich n and m each, independently of one another, denote 1 to 10.Preferably, n is 1 and m is 1 to 6.

The expression “fluorinated alkyl radical” preferably encompasses mono-or polyfluorinated radicals. Perfluorinated radicals are included.Preference is given to CF₃, CH₂CF₃, CH₂CHF₂, CHF₂, CH₂F, CHFCF₃ andCF₂CHFCF₃, particularly preferably CF₃.

The expression “fluorinated alkoxy radical” encompasses mono- orpolyfluorinated radicals. Perfluorinated radicals are preferred.Particular preference is given to the OCF₃ radical.

The expression “alk(en/yn)yl groups, in which one or more “—CH₂—” groupsmay be replaced by —O—” preferably relates to groups of this type inwhich a non-terminal CH₂ group is replaced. OH groups are included inthe general meaning.

The expression “substituted cycloalkyl” encompasses cycloalkyl which ismono- or polysubstituted by alkyl, in particular alkyl having 1 to 8carbon atoms.

The expression “substituted phenyl” encompasses phenyl which is mono- orpolysubstituted by a group defined like R¹, in particular phenyl whichis substituted by F, Cl, alkyl or alkoxy.

In the present application, high-frequency technology means applicationshaving frequencies in the range from 1 MHz to 10 THz, preferably from 1GHz to 3 THz, more preferably from 2 GHz to 1 THz, particularlypreferably from 5 to 300 GHz. The application is preferably in themicrowave spectrum or adjacent regions which are suitable for messagetransmission, in which phased-array modules can be used in transmittingor receiving antennae.

The liquid-crystal media according to the invention consist of one ormore compounds, preferably 2 to 30, more preferably 3 to 20 and verypreferably 3 to 16, compounds. These compounds are mixed in aconventional manner. In general, the desired amount of the compound usedin the smaller amount is dissolved in the compound used in the largeramount. If the temperature is above the clearing point of the compoundused in the higher concentration, it is particularly easy to observecompletion of the dissolution process. It is, however, also possible toprepare the media in other conventional ways, for example usingso-called pre-mixes, which can be, for example, homologous or eutecticmixtures of compounds, or using so-called “multibottle” systems, theconstituents of which are themselves ready-to-use mixtures.

All temperatures, such as, for example, the melting point T(C,N) orT(C,S), the transition from the smectic (S) to the nematic (N) phaseT(S,N) and the clearing point T(N,I) of the liquid crystals, are quotedin degrees Celsius. All temperature differences are quoted indifferential degrees.

In the present application and in the following examples, the structuresof the liquid-crystal compounds are indicated by means of acronyms,where the transformation into chemical formulae is carried out inaccordance with Tables A and B below. All radicals C_(n)H_(2n+1) andC_(m)H_(2m+1) are straight-chain alkyl radicals having n and m C atomsrespectively; n, m and k are integers and preferably denote 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11 or 12. The coding in Table B is self-evident.In Table A, only the acronym for the parent structure is indicated. Inindividual cases, the acronym for the parent structure is followed,separated by a dash, by a code for the substituents R¹*, R²*, L¹* andL²*:

Code for R¹*, R²*, L¹*, L²*, L³* R¹* R²* L¹* L²* nm C_(n)H_(2n+1)C_(m)H_(2m+1) H H nOm C_(n)H_(2n+1) OC_(m)H_(2m+1) H H nO.mOC_(n)H_(2n+1) C_(m)H_(2m+1) H H n C_(n)H_(2n+1) CN H H nN.FC_(n)H_(2n+1) CN F H nN.F.F C_(n)H_(2n+1) CN F F nF C_(n)H_(2n+1) F H HnCl C_(n)H_(2n+1) Cl H H nOF OC_(n)H_(2n+1) F H H nF.F C_(n)H_(2n+1) F FH nF.F.F C_(n)H_(2n+1) F F F nOCF₃ C_(n)H_(2n+1) OCF₃ H H nOCF₃.FC_(n)H_(2n+1) OCF₃ F H n-Vm C_(n)H_(2n+1) —CH═CH—C_(m)H_(2m+1) H H nV-VmC_(n)H_(2n+1)—CH═CH— —CH═CH—C_(m)H_(2m+1) H H

Suitable mixture components can be found in Tables A and B.

TABLE A

  BCH

  CBC

  CCH

  CCP

  CPTP

  CEPTP

  ECCP

  CECP

  EPCH

  PCH

  CH

  PTP

  CCPC

  CP

  BECH

TABLE B

  CBC-nmF

  PGP-n-m

  CGG-n-F

  CPGP-n-m

  PPGU-n-F

  GGP-n-F

  PGIGI-n-F

The following examples illustrate the present invention without limitingit in any way.

However, it becomes clear to the person skilled in the art from thephysical properties what properties can be achieved and in what rangesthey can be modified. In particular, the combination of the variousproperties which can preferably be achieved is thus well defined for theperson skilled in the art.

In the present application, unless expressly stated otherwise, theplural form of a term denotes both the singular form and the pluralform, and vice versa. Further combinations of the embodiments andvariants of the invention in accordance with the description also arisefrom the attached claims.

Abbreviations Used

-   MTB methyl tert-butyl ether-   SiO₂ silica gel-   RT room temperature (about 20° C.)

EXAMPLES

The acetylenes and boronic acids employed are commercially available orcan be prepared analogously to known syntheses which are known to theperson skilled in the art. The radicals “C₄H₉” stand for unbranchedn-butyl radicals. The same applies correspondingly to C₃H₇, C₆H₁₃, etc.

Synthesis Example 1 1.1 Synthesis of1-bromo-3-ethyl-4-(4-n-butylphenylethynyl)benzene

65 g (209 mmol) of 1-iodo-2-ethyl-4-bromobenzene and 38 g (226 mmol) of4-n-butylphenylacetylene are initially introduced in 300 ml of NEt₃, 1 g(5.3 mmol) of copper(I) iodide and 3.6 g (5.1 mmol) ofbis(triphenylphosphine)palladium(II) chloride are added, and the mixtureis stirred at RT for 2 h. The batch is cooled, water and heptane areadded, and the phases are separated. The organic phase is washed withsaturated sodium chloride soln., dried over sodium sulfate, filtered andevaporated in a rotary evaporator. The residue is purified by columnchromatography (SiO₂, heptane); the product is obtained as a colourlessoil.

1.2 Synthesis of 3-ethyl-4-(4-n-butylphenylethynyl)phenylboronic acid

63 g (180 mmol) of the bromide obtained in the preceding reaction areinitially introduced in 450 ml of tetrahydrofuran and cooled to −70° C.,and 125 ml (1.6 M in hexane, 200 mmol) of n-butyllithium are addeddropwise. After 1 h, 23 ml (203 mmol) of trimethyl borate in 50 ml oftetrahydrofuran are added, and the mixture is stirred at −70° C. for afurther 2 h and warmed to 0° C. The mixture is then worked up usingwater and 1 M hydrochloric acid, MTB is added, the phases are separated,and the aqueous phase is extracted once with MTB. The combined organicphases are washed with saturated sodium chloride solution, dried oversodium sulfate, filtered and evaporated in a rotary evaporator. Theresidue is washed by stirring with heptane and filtered off. The boronicacid is obtained as a colourless solid.

1.3 Synthesis of4-bromo-3-fluoro-3′-ethyl-4′-(4-n-butylphenylethynyl)biphenyl

16.8 g (162 mmol) of sodium carbonate and 14.9 g (49 mmol) of1-bromo-2-fluoro-4-iodobenzene are initially introduced in 60 ml ofwater and 75 ml of toluene and warmed to 70° C. 1.6 g (1.4 mmol) oftetrakis(triphenylphosphine)-palladium(0) and 15 g (49 mmol) of theboronic acid obtained in the preceding reaction in 50 ml of ethanol arethen added dropwise, and the mixture is heated under reflux for 16 h.Work-up is carried out by addition of MTB and water. The phases areseparated, and the aqueous phase is extracted twice with MTB. Thecombined organic phases are washed with saturated sodium chloridesolution, dried over sodium sulfate, filtered and evaporated in a rotaryevaporator. The residue is purified by column chromatography (SiO₂,heptane/toluene=9:1); the further purification is carried out byrecrystallisation from isopropanol.

1.4 Synthesis of3,4,5-trifluoro-2′-fluoro-3″-ethyl-4″-(4-n-butylphenylethynyl)-p-terphenyl(1)

3.3 g (31.1 mmol) of sodium carbonate and 5 g (11.5 mmol) of the bromideobtained in the preceding reaction are initially introduced in 15 ml ofwater and 60 ml of toluene and warmed to 70° C. 640 mg (0.55 mmol) oftetrakis-(tri-phenylphosphine)palladium(0) and 2.4 g (13.6 mmol) of3,4,5-trifluorophenyl-boronic acid in 25 ml of ethanol are then addeddropwise, and the mixture is heated under reflux for 16 h. Work-up iscarried out by addition of MTB and water, the phases are separated, andthe aqueous phase is extracted with MTB. The combined organic phases arewashed with saturated sodium chloride solution, dried over sodiumsulfate, filtered and evaporated in a rotary evaporator. The residue ispurified by column chromatography (SiO₂, heptane/toluene=9:1). Thefurther purification is carried out by recrystallisation from ethanol.

MS (EI): m/e (%)=486 (100, M⁺), 443 (40, [M-propyl]⁺).

C, 76; N, 159; I.

Δ∈=+16

Δn=0.35

γ₁=2.5 Pa·s

The following are synthesised analogously or comparably:

2.3-Fluoro-4-trifluoromethoxy-2′-fluoro-3″-ethyl-4″-(4-n-butylphenylethynyl)-p-terphenyl(2)

MS (EI): m/e (%)=534 (100, M⁺), 491 (45, [M-propyl]⁺).

C, 87; N, 198; I.

Δ∈=13

Δn=0.34

γ₁=2.8 Pa·s

3.3-Fluoro-4-cyano-2′-fluoro-3″-ethyl-4″-(4-n-butylphenylethynyl)-p-terphenyl

MS (EI): m/e (%)=475 (100, M⁺), 432 (43, [M-propyl]⁺).

C, 135; N, 262; I.

Δ∈=29

Δn=0.43

γ₁=18.0 Pa·s

4.3,5-Difluoro-4-trifluoromethoxy-2′-fluoro-3″-ethyl-4″-(4-n-butylphenyl-ethynyl)-p-terphenyl(4)

MS (EI): m/e (%)=552 (100, M⁺), 537 (7, [M-methyl]⁺), 509 (45,[M-propyl]⁺).

C, 87; N, 169; I.

Δ∈=17

Δn=0.33

γ₁=2.4 Pa·s

5.3,5-Difluoro-4-trifluoromethyl-2′-fluoro-3″-ethyl-4″-(4-n-butylphenyl-ethynyl)-p-terphenyl

MS (EI): m/e (%)=536 (100, M⁺), 521 (6, [M-methyl]⁺), 493 (50,[M-propyl]⁺).

C, 113; N, 144; I.

Δ∈=22

Δn=0.34

γ₁=3.4 Pa·s

6.3,4,5-Trifluoro-2′-fluoro-3″-ethyl-4″-(4-n-hexylphenylethynyl)-p-terphenyl

MS (EI): m/e (%)=514 (100, M⁺), 499 (6, [M-methyl]⁺), 443 (44,[M-pentyl]⁺).

C, 77; N, 144; I.

Δ∈=13

Δn=0.34

γ₁=2.7 Pa·s

7. 3,4,5-Trifluoro-3″-ethyl-4″-(4-n-butylphenylethynyl)-p-terphenyl

MS (EI): m/e (%)=468 (100, M⁺), 453 (8, [M-methyl]⁺), 425 (39,[M-propyl]⁺), 410 (21, [M-methyl-propyl]⁺).

C, 75; N, 184; I.

Δ∈=12

Δn=0.37

γ₁=2.2 Pa·s

8. 3,4-Difluoro-3″-ethyl-4″-(4-n-butylphenylethynyl)-p-terphenyl

MS (EI): m/e (%)=450 (100, M⁺), 435 (8, [M-methyl]⁺), 407 (35,[M-propyl]⁺), 392 (22, [M-methyl-propyl]⁺).

C, 106; N, 231; I.

Δ∈=7

Δn=0.40

γ₁=3.9 Pa·s

9.3,4,5-Trifluoro-2′-fluoro-2″-fluoro-3″-propyl-4″-(4-n-butylphenylethynyl)-p-terphenyl

MS (EI): m/e (%)=518 (100, M⁺), 503 (5, [M-methyl]⁺), 489 (26,[M-ethyl]⁺), 475 (16, [M-propyl]⁺), 461 (10), 446 (27).

Tg −31 C, 95; N, 105; I.

Δ∈=24

Δn=0.30

γ₁=2.7 Pa·s

10.4-(3,4,5-Trifluorophenylethynyl)-3-ethyl-2′-fluoro-4″-n-butyl-p-terphenyl

MS (EI): m/e (%)=486 (100, M⁺), 443 (66, [M-propyl]⁺), 428 (12,[M-methyl-propyl]⁺).

C, 89; N, 160; I.

Δ∈=18

Δn=0.35

γ₁=1.3 Pa·s

11.4-(3,4,5-Trifluorophenylethynyl)-3-ethyl-2′-fluoro-4′-n-butyl-p-biphenyl

MS (EI): m/e (%)=410 (100, M⁺), 395 (6, [M-methyl]⁺), 367 (74,[M-propyl]⁺), 352 (17, [M-methyl-propyl]⁺).

Tg −51 C, 25; I.

Δ∈=10

Δn=0.22

γ₁=0.2 Pa·s

12.4-(3,4,5-Trifluorophenylethynyl)-2-ethyl-2′,6′-difluoro-4′-n-butyl-p-biphenyl

MS (EI): m/e (%)=428 (100, M⁺), 413 (20, [M-methyl]⁺), 385 (39,[M-propyl]⁺), 370 (20, [M-methyl-propyl]⁺).

C, 59; I.

Δ∈=14

Δn=0.20

γ₁=0.2 Pa·s

13. 3,4,5-Trifluoro-3′,4′-(n-butylphenylethynyl)-p-biphenyl

MS (EI): m/e (%)=392 (100, M⁺), 377 (10, [M-methyl]⁺), 349 (84,[M-propyl]⁺), 334 (36, [M-methyl-propyl]⁺).

Tg −47 I

Δ∈=9

Δn=0.25

γ₁=0.3 Pa·s

Mixture Example 1

A liquid-crystal medium M-1 having the composition and properties asindicated in the following table is prepared. Compound (1) (No. 15)originates from Synthesis Example 1.

Composition Compound No. Abbreviation 1 BCH-3F.F 10.8% 2 BCH-5F.F 9.0% 3ECCP-30CF3 4.5% 4 ECCP-50CF3 4.5% 5 CBC-33F 1.8% 6 CBC-53F 1.8% 7CBC-55F 1.8% 8 PCH-6F 7.2% 9 PCH-7F 5.4% 10  CCP-20CF3 7.2% 11 CCP-30CF3 10.8% 12  CCP-40CF3 6.3% 13  CCP-50CF3 9.9% 14  PCH-5F 9.0%15  (1) 10.0% Σ 100.0% Physical properties T(N, I) = 96° C. Δn (20° C.,589.3 nm) = 0.124 Δε (20° C., 1 kHz) = 4.9 γ₁ (20° C.) = 166 mPa · s

This mixture is used for applications in the microwave region, inparticular for phase shifters for phased-array antennae.

For comparison, a medium C-1 without component (1) is prepared fromcompound Nos. 1-14 of medium M-1, where compound Nos. 1-14 are presentin the same relative amounts.

Mixture Examples 2 and 3

Liquid-crystal media M-2 and M-3 having the composition of M-1 areprepared with the difference that for M-2, compound (2) from SynthesisExample 2 is employed instead of compound (1), and for M-3, compound (4)from Synthesis Example 4 is employed instead of compound (1).

The results for the mixture examples are shown in the following table.

TABLE Properties of mixtures M-1, M-2, M-3 and C-1 (comparison) at 19GHz (20° C.) Mixture ε_(r,) | | ε_(r, ⊥) τ tan δ_(ε, r,) | | tanδ_(ε, r, ⊥) η M-1 2.63 2.29 0.130 0.0045 0.0116 11.2 M-2 2.64 2.31 0.1270.0047 0.0129 9.82 M-3 2.62 2.30 0.125 0.0046 0.0119 10.46 C-1 2.56 2.290.107 0.0049 0.0126 8.50

The tuneability τ and the material quality η are significantly improvedfor mixtures M-1, M-2 and M-3 compared with comparative mixture C-1.

The invention claimed is:
 1. A compound of formula I

in which H/F means H or F, A¹⁻⁵ independently of one another, denote a)1,4-phenylene, in which one or more CH groups are optionally replaced byN, or b) a radical of one of the following formulae

 wherein in a) and b), optionally one or more H atoms are independentlyreplaced by L, which L in a) and b) each, independently of one another,denotes Br, Cl, F, CN, —NCS, —SCN, SF₅, C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy,C₃-C₆ cycloalkyl or a mono- or polyfluorinated C₁-C₁₀ alkyl or alkoxygroup, and wherein one of the rings A³ and A⁴ denotes

Y denotes S or O, R¹ denotes a halogenated or unsubstituted alkylradical having 1 to 15 C atoms, in which one or more CH₂ groups areoptionally replaced, independently of one another, by —CH═CH—, —CF═CF—,—CF═CH—, —CH═CF—, —(CO)O—, —O(CO)—, —(CO)—, —O— or —S— in such a waythat O or S atoms are not linked directly to one another, or denotes F,Cl, Br, CN, SCN, NCS or SF₅, X denotes F, Cl, Br, CN, SCN, NCS, SF₅ or ahalogenated alkyl radical having 1 to 15 C atoms, in which one or moreCH₂ groups are optionally replaced, independently of one another, by—CH═CH—, —CF═CF—, —CF═CH—, —CH═CF—, —(CO)O—, —O(CO)—, —(CO)—, —O— or —S—in such a way that O or S atoms are not linked directly to one another,Z¹, Z², Z⁴, Z⁵ all denote a single bond, and m, n, p, q independentlydenote 0 or 1, where m+n+p+q is 1, 2, 3 or
 4. 2. A compound according toclaim 1, wherein A³ denotes 1,4-phenylene, in which one or more CHgroups are optionally replaced by N.
 3. A compound according to claim 1,wherein m and n are
 0. 4. A compound according to claim 1, wherein A¹,A², A⁵ and one of A³ or A⁴, if present, each denote an optionallysubstituted 1,4-phenylene ring.
 5. A compound according to claim 1,wherein m+n+p+q is
 1. 6. A liquid-crystal medium, comprising one or morecompounds according to claim
 1. 7. A liquid-crystal medium according toclaim 6, further comprising one or more compounds of formula II:

in which: L¹¹ denotes R¹¹ or X¹¹, L¹² denotes R¹² or X¹², R¹¹ and R¹²independently of one another, denote unfluorinated alkyl orunfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl,unfluorinated alkynyl, unfluorinated alkenyloxy or unfluorinatedalkoxyalkyl having 2 to 15 C atoms, X¹¹ and X¹² independently of oneanother, denote F, Cl, Br, CN, NCS, SCN, SF₅, or fluorinated alkyl orfluorinated alkoxy having 1 to 7 C atoms, or fluorinated alkenyl,fluorinated alkenyloxy or fluorinated alkoxyalkyl having 2 to 7 C atoms,p, q independently denote 0 or 1, Z¹¹ to Z¹³ independently of oneanother, denote trans-CH═CH—, trans-CF═CF—, —C≡C— or a single bond, and

 independently of one another, denote

L′ independently denotes branched or unbranched alkyl, alkenyl oralkynyl having 1 to 12 C atoms, in which, independently of one another,one or more CH₂ groups are optionally replaced by O, or denotes C₃-C₆cycloalkyl, C₃-C₆ cycloalkenyl, fluorinated alkyl or alkenyl,fluorinated alkoxy or alkenyloxy, F, Cl, Br, CN, NCS, SCN or SF₅.
 8. Aliquid-crystal medium according to claim 6, wherein the concentration ofthe compounds of formula I in total is 5% to 95%.
 9. A process forpreparing a liquid-crystal medium according to claim 6, comprisingmixing together one or more compounds of formula I with one or morefurther compounds and optionally with one or more additives.
 10. Acomponent for high-frequency technology, which contains a liquid-crystalmedium according to claim
 6. 11. A component according to claim 10,which comprises one or more functionally connected phase shifters.
 12. Aphased array antenna, which comprises one or more components accordingto claim
 10. 13. A compound according to claim 1, wherein L each,independently of one another, denotes methyl, ethyl or straight orbranched propyl.
 14. A compound according to claim 1, wherein L each,independently of one another, denotes cyclopropyl.
 15. A compoundaccording to claim 1, wherein one of the rings A³ and A⁴ denotes


16. A compound according to claim 1, wherein one of the rings A³ and A⁴denotes


17. A compound according to claim 1, wherein one of the rings A³ and A⁴denotes


18. A compound according to claim 1, wherein R¹ denotes an unsubstitutedalkyl radical having 1 to 15 C atoms, in which one or more CH₂ groupsare optionally replaced, independently of one another, by —CH═CH—,—CF═CF—, —CF═CH—, —CH═CF—, —(CO)O—, —O(CO)—, —(CO)—, —O— or —S— in sucha way that O or S atoms are not linked directly to one another, ordenotes F, Cl, Br, CN, SCN, NCS or SF₅.
 19. A compound according toclaim 1, wherein X denotes F, Cl, Br, SCN, NCS, SF₅ or a halogenatedalkyl radical having 1 to 15 C atoms, in which one or more CH₂ groupsare optionally replaced, independently of one another, by —CC—, —CH═CH—,—CF═CF—, —CF═CH—, —CH═CF—, —(CO)O—, —O(CO)—, —(CO)—, —O— or —S— in sucha way that O or S atoms are not linked directly to one another.
 20. Acompound according to claim 1, wherein m+n is 0 or 1.